The anchorage is east of a reef that that runs between the islands and can, reputedly, occasionally dry.
Although it has the reputation for being an "occasional" anchorage, it is regularly used overnight, very often by boats waiting for a favourable tide for the Sound of Luing, or the Corryvreckan. It is well sheltered from, clockwise, the SE to NW.
The bay looks deceptively small when entered from the north, and its size is only really appreciated from the islands. Watch out for rocks awash (charted) if approaching from the north - we generally hold close to the east side of Eilean Dubh Beag on this approach. There is also a narrow approach passage from the east, between Eilean Dubh Mòr, and the offlying Sgeir a' Gheòidh.
The holding is good (sand), although care should be taken to ensure that the anchor is well dug in (the rocks look very close).
The anchorage looks towards the west over the reef, but gives surprisingly good shelter against the prevailing wind. We have anchored overnight in westerly F5s, with a bit of six. Although completely open to the west at high tide, there was very little swell, the reef between the islands sufficiently breaking up the waves.
There are two caves on Eilean Dubh Mor. We found one of them, a "room and kitchen" with comfortable well sheltered sleeping accommodation. Both islands are used as adventure training areas for kids.
A word of caution - an anchor light is necessary at night as fishing boats use the channel as a short cut. The passage is navigable to shoal draught boats skippered by those who know the local waters well.
I would not advise attempting to take a deeper keeled boat through, and I wouldn't even tdream of trying it with Shard, but I was well impressed with Silver Surf coming through from the west at mid tide;
If nothing else, the ease of Silver Surf's passage demonstrates the necessity of showing an anchor light.
